apt-proxy is a useful tool to stop you having to download APTs for every machine on your network.
deb http://myserver:9999/debian stable main contrib non-free deb http://myserver:9999/debian-non-US stable/non-US main contrib non-free deb http://myserver:9999/security stable/updates main contrib non-free
Then continue to use apt-get as you always have.
I would recommend editing the configuration file under /etc/apt-proxy/ to add a nz server as first choice as it can be slow getting updates from the US at times.
If you have problems with this then there is also apt-cacher that you can use.
# apt-get update 0% [Waiting for headers]